Field of the Invention
The present invention relates to an imaging device and an imaging system.
Description of the Related Art
In a CMOS image sensor, imaging by using a global electronic shutter operation is proposed in recent years. An imaging device with a global electronic shutter function is described in Japanese Patent Application Laid-Open No. 2004-111590 and Japanese Patent Application Laid-Open No. 2006-246450. The imaging device with a global electronic shutter function has an advantage that a subject image is unlikely to be distorted even when a subject moving at a high speed is photographed.
More enhanced functions are demanded in the imaging device with a global electronic shutter function, such as an extension of a dynamic range by multiple exposures and an increase in the speed of focus detection on an imaging surface. However, a configuration or a driving method of the imaging device suitable for the enhanced functions is not examined in the conventional imaging device.
In photographing of moving images using the imaging device with the global electronic shutter function, a function of taking images by changing an exposure period in each frame is demanded in some cases in order to handle a change in the luminance of a photographing scene. In such a case, intervals between centers of the exposure periods of the frames are not constant, and an image quality degradation called jerkiness with unnatural motion of a moving subject may occur.